APPLICATION OF URETHRAL INSTABILITY AS A PROGNOSTIC TOOL TO PREDICT THE SUCCESS OF INTERSTIM SACRAL NERVE STIMULATION

T.B. McKinney, E.A. Hashemi

University Executive Campus, Turnersville, NJ

OBJECTIVE: A retrospective chart review of all InterStim sacral nerve stimulation patients for possible predictive value of success was undertaken. We were particularly interested in looking for urodynamic indicators for success with urethral instability (urethral pressure variations of greater than 15 cmH2O pressure off of baseline during filling phase) being evaluated carefully. This paper reports the success of InterStim in relation to urethral instability. 

MATERIALS AND METHODS: Chart reviews and retrospective analysis of patient’s urodynamics were applied, using Medtronics multi P urodynamic machine and dual sensor T-DOC “air charged” urodynamic catheters. A total of 24 patients in our office underwent baseline assessment, urodynamic evaluation, and sacral nerve stimulation at S3 using InterStim system (Medtronics, Inc., Minneapolis, Minnesota). All patients had undergone prior conventional treatments such as pharmacotherapy and/or surgical intervention for voiding dysfunction.

RESULTS: 21 patients had urethral instability documented on their urodynamics. Two patients had poor studies and could not use their data. All 24 patients had InterStim placed with an overall success rate of 83 % (20 out of 24). In looking at the success of InterStim with cross-reference to urethral instability as predictor, 18 of successes had urethral instability (86 %). Three had failure with urethral instability; however, one had retention with an atonic bladder as reason for InterStim placement. One patient with negative urethral instability had negative response to InterStim.

CONCLUSIONS: Urethral instability can be used as a prognostic tool in giving an increased clinical predictive value for success of InterStim. A future prospective research using pre and post op urodynamics as a tool can help to further measure and determine the efficacy of InterStim in relation to urethral instability and whether urethral instability disappears with successful InterStim placement. In our series of one that had repeat urodynamic after InterStim the urethral instability disappeared. This may be an exciting indicator of success. Looking at patients with frequency/urgency syndrome without urethral instability that did not go to InterStim, they had either good responses to anticholinergics or went on to have interstitial cystitis with hydrodistension and interstitial cystitis protocols. This may indicate a new triage for differentiating interstitial cystitis from a neurogenic origin to frequency and urgency. These will be looked at in a follow up paper.

Key Words: urethral instability, InterStim, interstitial cystitis 

Disclosure – Nothing to disclose.